Loudspeaker



Sept. 26, 1939. H. JYRCH LOUDSPEAKER Filed Jan. 15, 1938 Patentedsepti26,

UNITED STATES PATENT OFFICE Application In 4 Claims.

This invention relates to a loud-speaker for loud-speaker installationson railway platforms etc. It has for its object to reduce as much aspossible the transmission of sound to neighbour- 5 ing platforms, thusdirecting the sound towards the platform itself, and this is attained bythe fitting of the loud-speaker to the back of a tubular member opentowards the front, which is somewhat inclined to the horizontal so thatthe desired directive effect is attained. It is further improved by theprovision of a broad slot in this tubular member on its underside.Preferably, downwardly bent guide surfaces are fitted, e. g. attached tothe edges of the slots.

In this manner the low speech frequencies, which are not capable ofbeing confined, immediately balance themselves out downwards I throughthe slot provided and can, as in effect, be short-circuited. Experimentshave shown that in this way considerably better clarity and directionalcharacteristics result. A further advantage of this method is to be seenin the fact that there is also good clear distribution in the region ofthe platform directly under the loud-speaker. There is very little sidesound spreading, because the slot directs the sound through the guidesurfaces there provided. In the case of long platforms it is anadvantage to install several loud-speakers at about 20 metres apart. Forthis purpose the electro-mechanical part, e. g. a cone reproducer, isarranged in the center of a tubular member, which preferably consists oftwo casing sections extending to opposite sides oflthe cone.

a different inclination, i. e., the rear part a steeper inclination thanthe front part, so that one section transmits about one-third and theother about, two-thirds of the entire length of the transmitting range.If two such loud-' speakers are arranged at a distance apart of about 20metres, the rear part of the casing having the steeper inclination is so.directed that the sound fades out at about one-third of the distancefrom the casingconstituting the front part of the next loud-speaker,whereas the said front part of the neighbouring loudspeaker coverstwo-thirds of this distance. It follows therefrom as an advantage of. anessential part of the inventive idea, viz.,the inclination of bothparts. that the transmitting beams of the tubular member do not traversethe line connecting the two loud-speakers, thus the clarity of theinstallation is much improved.

Embodiment of the invention is illustrated in the drawing, in which Itis advantageous to give both parts of the'casing January 15, 1938,Serial No. 185,110 "Germany November 25, 1936 Fig. 1 shows theloud-speaker from the side,

Fig. 2 from below.

Here the loud-speaker is so constructed that it transmits the sounds toboth ends. Two tubular members, I and 2, having the flanges F and Fsupport the flange 3 of the membrane or diaphragm of the loud speaker.That is to say, the flanges F and F clamp the membrane or a part thereofbetween the same and suitable bolts B may be used for connecting theflanges F and F in the conventional manner. The said tubular members Iand 2 are obliquely cut at I a and 2a and are provided in their lowerpart with a slot lb, 2b respectively. These slots are bounded laterallyby a guide surface lo and 2c respectively.

As shown in Fig. l, the inclination of the tubular member 2 to thehorizontal is greater than the inclination of the tubular member I. Thisdegree of inclination depends on the distance from each other of twoloud-speakers. The inclination is preferably so chosen that the part 2has a range of one-third and the part I twothirds of the complete lengthof the transmitting range. Practical experiments with such meas;-urement have given extraordinarily good clarity and the smallestpossible lateral transmission towards the neighbouring platform.

From the foregoing it will be apparent, that the present inventionrelates to a loud-speaker of the public address type, which hasparticular adaptability to use in connection with the loading platformsin railway stations. In a situation of this kind it is desirable to havethe announcement heard on a particular platform in such a way, that itcannot be distinctly heard on an opposing platform, so that passengerscannot become confused. To that end it is proposed to support or suspenda number of units constructed in accordance with the present inventionat predetermined intervals along the platform in such a way, that speechsounds emanating from the series of loud-speakers will be hearddistinctly along the line of the platform. To obtain this result, it isdesired, as previously set forth, to downwardly incline the oppositetubular sections of the loud-speakers, so that the sounds emanating fromone will not conflict substantially with sounds emanating from theother. It will be apparent, that the degree of inclination will bevaried according to the spacing of the loudspeakers along the platform,as, for example, according to the illustration previously given.

I claim:

.1. A sounddirecting construction for loudspeakers of the public"address type, including in combination, an electro-mechanical soundreproducingunit, and a pair of oppositely extending downwardly inclinedtubular casings, located one at each side of said imit, said casingsbeing of substantially uniform diameter throughout and npen at theirouter ends, the bottom portion of each casing being provided with a slotextending inwardly from its open end to permit 10w speech frequencies toescape downwardly before reaching the said open end.

2. A device as set forth in claim 1, wherein one casing is of shorterlength than the other, said casing of shorter length having a greaterdown ward inclination than said other sections thereby to provide adiiferential sound transmitting range between the casings.

3. A device as set forth in claim 1, wherein the slot in each casing isprovided at opposite sides thereof with sound directing flanges.

4. A sound directing construction for loudspeakers of the public addresstype particularly adapted to be supported above a railway stationplatform, including in combination, an electromechanical soundreproducing unit and tubular casing sections located one at each side ofsaid unit, said sections being inclined downwardly from the unit towardthe platform and each having a slot at its bottom side.

HERBERT JYRCH.

